Future availability has always been a major concern for me in regards to the 5.45. All it will take is a stroke of the (Presidential) pen for imports to cease.
The 7.62 has an established manufacturing and fan base. With Winchester, Federal and Remington all making ammo its future availability is more assured.

I'm sure that with as many AK74s in the US today if the President signed a ban on the import of ammo, the ammo manufacturing co.s in the US would pick up the making of the 5.45x39 ammo to fill the demand.

7.62x39mm most common round in the world. no matter what anyone ever tells you and not really that bad on price if you get some of the middle range stuff. the cheap stuff tends to be dirty(leave more residue) and i just spend more time cleaning everything. not that the weapon cant handle it. i just keep them all good and clean. if you buy remington or winchester yeah it adds up quick but inside 300m not really all that different from a .308 and rounds are cheaper than that all day.

Of the choices mentioned by the OP I think I'd go with the Tantal, (from the web):
1) The gas tube is floated between the gas block and the rear sight support. It does not touch the handguard. The handguard is supported by an extended lower handguard flange and the rear sight support.
2) The muzzle brake has been modified to also function as a grenade launcher.
3) The Tantal comes with a side-folding stock that mounts just like a fixed buttstock. It does not require a different rear trunnion, but mounts on a standard trunnion in the normal fashion. It can be quickly and easily interchanged with a fixed stock. Most military sidefolding stocks are build on dedicated receivers, and cannot be converted to fixed stocks.
4) The gas block has been modified to accept a bipod. Standard NATO bipods will fit this version.
It also has a cold hammer forged chrome plated bore barrel and the reputation of being one of the best made AK's on the current market...